Taste and Odor Questions About Drinking Water Stemming From Geosmin

The City of Henderson is committed to delivering safe, high-quality drinking water to all businesses and residents we serve. The water you are receiving meets or exceeds all Environmental Protection Agency drinking water Primary Standards (addressing health and safety). The EPA has established another set of standards that specifically address aesthetics known as Secondary Standards.

Water samples collected in early January exceeded the Secondary Standard set for the Threshold Odor Number (TON). The TON analysis is an odorous test which is conducted to determine different smells coming from the water. Additional sampling has confirmed that the TON exceedance is being caused by Geosmin within the source water.

Geosmin is a harmless compound produced by some species of algae in source water and the frequency of occurrence for these types of events is known to increase during droughts. As a comparison, beets contain up to 4,000 times the concentration of Geosmin, which is what gives the vegetable its earthy smell. Geosmin is not visible and produces no color change to the water. There is no detectable presence of the algae that produces Geosmin in our water supply.

Although the concentrations of Geosmin are extremely low in the parts per trillion range (one square inch in 250 square miles), it is not uncommon for the average person to detect the presence of this compound at these extremely low concentrations. The most common complaint related to these occurrences is an “earthy or musty” smell. Most individuals will notice the earthy/musty odor more predominately in their hot water supply.

The City is actively monitoring for Geosmin, however it is very difficult to remove at these low concentrations. The duration of this event is unknown, however historically they have lasted a number of weeks.

The City of Henderson, in coordination with the Southern Nevada Water Authority, takes 180 samples per month from the water system to ensure it is safe. Although the odor may be unpleasant to some, the water is safe to consume and poses no health risks.